Pneumatic tires are commonly used on a variety of vehicles, such as passenger automobiles, aircraft, and industrial machinery. It is well known that even a small amount of imbalance in a pneumatic tire mounted to a vehicle can cause undesirable vibration and noise when the tire is rotating at the operating speeds of the vehicle. This imbalance may be attributed to non-uniformities or imperfections in the tire wheel rim, or to imperfections or non-uniformities in the molded tire itself. Such imbalance is particularly noticeable on tires used on aircraft landing gear, due to the high wheel speeds attained during take-off and landing of the aircraft.
One approach to eliminating or reducing the effects of imbalance in formed tires has been to secure discrete patches of rubber material to the tire inner liner, after the tire has been cured, in an effort to offset any imbalances. This approach requires determining the amount and location of imbalance of the formed tire, typically in a dynamic testing machine. Based upon the results of the imbalance testing, a determination is made as to the location and mass of the patch material needed to counteract the imbalance of the tire. The inner surface of the tire is thereafter cleaned at the appropriate location, typically using an organic solvent, and the patch is adhered at the desired location using adhesive material. Rubber patches commonly used for balancing tires are generally provided in fixed weight increments, thereby limiting the precision to which the imbalance may be corrected, and requiring users to maintain an inventory of patches in various sizes. Alternatively, fluidic balancing materials can be applied to the inner surface of the cured tire, where the fluidic balancing materials become more viscous post-application and remain substantially affixed where it had been applied to the inner surface, as described in commonly-assigned U.S. Pat. No. 7,368,024. These fixed weight methods require post-cure processing.
Another conventional system utilizes a free-flowing balancing material, such as glycol and fibers, within the imbalanced tire. The material may be introduced at mounting of a tire on a rim or into an already mounted tire. The tire retains proper balance because the free-flowing material, specifically the minuscule individual elements making up the free-flowing material, inside the tire are distributed by centripetal forces generated by rotation of the wheel/tire in such a way that the free-flowing material balances a heavy spot or a heavy side of the tire assembly. However, when the rotation stops, the material flows under the force of gravity and the process of re-balancing will recommence after every stop. As such, a certain degree of vibration will be felt in the vehicle before the rebalancing is completed. Furthermore, during tire repair or tire retreading, the free flowing material may come out and may need to be refilled.
Accordingly, there remains a need for a self-balancing pneumatic tire, and a method of making the same, that overcomes the aforementioned drawbacks and disadvantages.